I have not been able to find a pointing device that I liked out of the box. Because I like the ergonomics of a tray, the limited travel available on a tray limits me to stationary devices. When I have to use a mouse for extended periods, the humble 10 dollar joy/wow pen has great ergonomics for those that require less wrist pronation.
I like trackballs but don't like the feel of the thumb operated ones although some people do. I have severe arthritis in my thumbs and wrists and limited feeling in them, so I found the Logitech m570 akin to torture, comfortable to hold but not to use. Too bad, it seems like a nice trackball for the right user.
I really like the action of large Kensington trackballs. Out of the box, I prefer the switch action of the Expert Mouse over the Slimblade but the Slimblade's smoother scrolling won me over. The Slimblade's lower profile is another draw, reducing the wrist extension necessary in use. I just think the switch feel leaves a lot to be desired; it seems to have a large target but a small sweet spot for comfortable switching.
Anyone that would require less wrist pronation might have an issue with most finger operated trackballs. In order to reach the switches the hand needs to be almost level with the table. That didn't work for me well at all. My solution was to inset the trackball into the work surface.
http://flic.kr/s/aHsjFazJhh This solved all of my ergonomic issues but in two different ways. The side mount arrangement lowers the unit and has a tilt that puts the trackball face in better alignment with the natural position of my hand. The center mount Slimblade has satellite switches that are well positioned and don't require an overly pronated hand.